The Pinyon Jay (Gymnorhinus cyanocephalus) is closely associated with piñon–juniper woodlands in the Intermountain West and Southwest regions of the United States. It is of conservation concern, given it is one of the landbirds declining the fastest and most persistently in these regions, at an average rate of –3.6% from 1968 to 2015, according to the Breeding Bird Survey. Despite the population’s falling by >50% over this period, the Pinyon Jay has not been widely studied, and little is known about the factors responsible for its diminishing numbers. Although the Pinyon Jay’s rate of decline exceeds that of the Greater SageGrouse (Centrocercus urophasianus)—a species targeted for significant conservation efforts—no comprehensive effort designed to benefit this jay has been implemented. Current management in Great Basin piñon–juniper woodlands includes removal of trees to create or protect shrublands for the benefit of sage-grouse and other sagebrush-associated wildlife, and southwestern piñon–juniper woodlands are being thinned for fuels reduction or management of other wildlife. The effect of these treatments on the Pinyon Jay and other piñon–juniper birds, however, has been little studied. Thus further research is needed to clarify the causes of the jay’s decline, develop habitat models for this and other piñon–juniper species, and devise approaches for management of piñon–juniper woodland that balance the interests of the Pinyon Jay and other species of concern, including the Greater Sage-Grouse.
One possible link between livestock grazing and bird population declines is variation in nest predation rates. To explore this possibility we documented vegetational differences in a montane riparian community subdivided by a fence, one side of which traditionally has been summer-grazed, and the other side rested from grazing for 30 years. We found that ground vegetation was more abundant, willows (Salk spp.) less abundant, and vertical vegetational diversity was lower on the grazed relative to the rested side. Predation rates on real nests were higher on the grazed side compared to the rested side. Artificial nests were placed (1) in mixed conifer vegetation to mimic the most common nest types currently present in the riparian zone, (2) in streamside willows that differed in abundance across the fence, and (3) in old-willow remnants distant from the stream, which were equally abundant on both sides of the fence. All artificial above-ground nests, and ground nests in the old-willow experiment, suffered greater predation rates on the grazed compared to the rested side. Thus, livestock grazing may not only affect availability of nesting substrates for riparian birds by reducing streamside vegetation, but could influence bird populations by facilitating nest predation, possibly by increasing detectability of nests or through changes in predator assemblage.
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